[Cbe-oss-dev] [PATCH 3/6] cell: add hardcoded spu vicinity information for CBPW

[Arnd Bergmann]

On Monday 12 February 2007 02:13, Andre Detsch wrote:
> Subject: cell: add hardcoded spu vicinity information for CBPW
> From: Andre Detsch <adetsch at br.ibm.com>
> 
> This patch allows the use of spu affinity on CPBW platform, whose
> original FW does not provide affinity information.
> This is done through two hardcoded arrays, and by reading the reg
> property from each spu.

The name of the platform is not CPBW, but QS20, we should really
call it that, both in the comments and in the code.

> +static void init_aff_CPBW_harcoded(void)
> +{
> +       int node, i;
> +       struct spu *last_spu, *spu;
> +       u32 reg;
> +
> +       for (node = 0; node < MAX_NUMNODES; node++) {
> +               last_spu = NULL;
> +               for (i = 0; i < SPES_PER_BE; i++) {
> +                       spu = spu_lookup(node, "reg", CPBW_reg_idxs[i]);
> +                       if (!spu)
> +                               continue;
> +                       reg = *(u32 *)get_property(spu->devnode, "reg", NULL);
> +                       spu->has_mem_affinity = CPBW_reg_memory[reg];
> +                       if (last_spu)
> +                               list_add_tail(&spu->aff_list,
> +                                               &last_spu->aff_list);
> +                       last_spu = spu;
> +               }
> +       }
> +}

Hmm, not sure if this is safe. The meaning of the "reg" property has
changed in current firmware. While this is currently not shipping
to customers, there is an internal version of the QS20 firmware that
puts the register addresses into the "reg" properties, instead of the
spu numbers. If the above code ever runs on such a system, it will get
overrun the CPBW_reg_idxs array and bad things happen.

You can probably assume that the new firmware would have proper
vicinity information though.

> @@ -696,6 +738,11 @@ static int __init init_spu_base(void)
>  
>         xmon_register_spus(&spu_full_list);
>  
> +       root = of_get_flat_dt_root();
> +       if (of_flat_dt_is_compatible(root, "IBM,CPBW-1.0") ||
> +           of_flat_dt_is_compatible(root, "IBM,CPBW-SystemSim"))
> +               init_aff_CPBW_harcoded();
> +

I'd suggest that you first check if the properties are there,
before you search for the hack to do on IBM,CPBW-1.0.

I'm not really sure how to handle SystemSim. Does it even simulate
different access patterns based on the location of the SPU? If not,
we should not try to fake anything here. If anything, it should
be up to the simulation to create the vicinity properties for
the simulated hardware, based on user decisions.

	Arnd <><